The research described in this application is designed to address diagnostic and treatment problems associated with infection in 3 separate types of orthopaedic patients. The first type is those that have injuries in which the wound is open and probably contaminated with many bacteria. The problem of infections in orthopaedic surgery is of special interest because of the use of foreign bodies in the management of fractures. One decision involves whether or not to close a wound with sutures. The second decision is whether or not to use internal fixation devices in the presence of a possibly contaminated field. Laboratory procedures that would quickly inform the surgeon of the level of bacterial contamination would aid in these decisions. Scientific evidence of the role of internal fixation in high rates of infection would also help. Quantitative wound culture studies are proposed to answer the question as to whether or not there are increased rates of infection with the use of internal fixation. The second type is those individuals who develop infections many months after an implant or total joint was inserted. The question to be addressed in this situation is whether or not the existence of a sensitivity to one or more of the components of the implant might contribute to the likelihood of an infection. The third type of patient is those in whom the diagnosis of the etiologic agent is difficult because the appropriate sample for bacteriologic culture is difficult to obtain or because there are antibacterial substances in the specimen. The use of rapid immunologic techniques is proposed to aid in the rapid diagnosis of septic arthritis and osteomyelitis. The studies proposed in this application should aid the orthopaedic surgeon in patient management decisions.